Ocular implants and methods for their manufacture

Abstract

A method for modifying a PMMA surface by the gamma-irradiation induced polymerization thereon of N-vinylpyrrolidone, 2-hydroxyethylmethacrylate or a mixture thereof while maintaining the following conditions: (a) monomer concentration in the range of from about 0.5% to about 50%, by weight; (b) total gamma dose in the range of from about 0.01 to less than about 0.50 Mrad; (c) gamma dose rate in the range of from about 10 to about 2500 rads/minute; and (d) maintaining the molecular weight of the polymer in solution in the range of from about 250,000 to about 5,000,000. The invention also relates to modifying polypropylene, polyvinylidene fluoride, polycarbonate and silicon surfaces according to a similar method as well as materials produced by the above methods which are useful as ocular implants.

We claim: 
     
       1. In a method for modifying the surface of an ocular implant material, said surface consisting essentially of polymethylmethacrylate (PMMA), by the one-step, gamma-irradiation induced polymerized, chemically grafted coating thereon of N-vinylpyrrolidone (NVP), 2-hydroxyethylmethacrylate (HEMA) or a mixture of (NVP) and (HEMA) so as to form a thin, hydrophilic coating of (1) poly-N-vinylpyrrolidone (PVP), (2) poly-2-hydroxyethylmethacrylate (PHEMA), or (3) a copolymer of NVP and HEMA on said surface, the improvement consisting essentially of conducting said one-step, gamma-irradiation induced graft polymerization in a substantially aqueous solution under the following conditions: (a) monomer concentration in the range of from about 0.5% to about 50%, by weight;   (b) total gamma dose in the range of from about 0.01 to less than about 0.50 Mrad;   (c) gamma dose rate in the range of from about 10 to about 2500 rads/minute; and   (d) maintaining the molecular weight of the polymer in solution in the range of from about 250,000 to about 5,000,000.   
     
     
       2. The method of claim 1 further including one or more of the following conditions: (e) substantially excluding free oxygen from said graft polymerization solution;   (f) maintaining the thickness of said polymer coating in the range of from about 100 Å to about 100 microns;   (g) including a free radical scavenger in said aqueous graft polymerization solution; and   (h) including in said aqueous graft polymerization solution a swelling solvent for said PMMA surface.   
     
     
       3. The method of claim 1 or 2, wherein said ocular implant material is an intraocular lens. 
     
     
       4. The method of claim 1 or 2, wherein said ocular implant material is a corneal inlay. 
     
     
       5. The method of claim 1 or 2, wherein said ocular implant material is a keratoprosthesis. 
     
     
       6. In a method modifying the surface of an ocular implant material, said surface consisting essentially of polypropylene (PP) polyvinylidene fluoride (PVDF), a polycarbonate (PC) or a silicone (PSi), by the one-step, gamma-irradiation induced polymerized, chemically grafted coating thereon of N-vinylpyrrolidone (NVP), 2-hydroxyethylmethacrylate (HEMA) or a mixture of NVP and (HEMA) so as to form a thin hydrophilic coating of (1) poly-N-vinylpyrrolidone (PVP), (2) poly-2-hydroxyethylmethacrylate (PHEMA) or (3) a copolymer of NVP and HEMA on said surface the improvement consisting essentially of conducting said one-step, gamma-irradiation induced graft polymerization in a substantially aqueous solution under the following conditions: (a) monomer concentration in the range of from about 0.5% to about 50% by weight;   (b) total gamma dose in the range of from about 0.01 to less than about 0.50 Mrad;   (c) gamma dose rate in the range of from about 10 to about 2500 rads/min;   (d) maintaining the molecular weight of the polymer in solution in the range of from about 250,000 to about 5,000,000; and   (e) substantially excluding free oxygen from said aqueous graft polymerization solution.   
     
     
       7. The method of claim 6 further including one or more of the following conditions: (f) maintaining the thickness of said polymer coating in the range of from about 100 Å to about 100 microns;   (g) including a free radical scavenger in said aqueous graft polymerization solution; and   (h) including in said aqueous graft polymerization solution a swelling solvent for said surface.   
     
     
       8. The method of claim 1, 2, 6 or 7 wherein said NVP, HEMA or mixture of NVP and HEMA is gamma-irradiation induced co-polymerized with an ionic monomer or mixture thereof under said conditions, the total monomer concentration in said solution being in the range of from about 1% to about 50%, by weight and maintaining the molecular weight of the resultant copolymer in solution of NVP, HEMA or mixture of NVP and HEMA and said ionic monomer or mixture thereof in the range of from about 250,000 to about 5,000,000. 
     
     
       9. The method of claim 8 wherein said ionic monomer is a vinylsulfonic acid or a vinylcarboxylic acid. 
     
     
       10. The method of claim 9 wherein said vinycarboxylic acid is acrylic, methacrylic or crotonic acid. 
     
     
       11. The method of claim 8 wherein said ionic monomer is an amino-functional monomer. 
     
     
       12. The method of claim 11 wherein said amino-functional monomer is a vinylpyridine, an aminostyrene, an aminoacrylate or an aminomethacrylate. 
     
     
       13. An ocular implant material prepared according to the method of claim 1, 2, 6, 7 or 8. 
     
     
       14. An ocular implant according to claim 13 wherein said ocular implant is an intraocular lens, a corneal inlay, a keratoprosthesis, an epikeratophakia device, a glaucoma drain, a retinal staple or a scleral buckle.